In the oil and gas industry the storage tanks for crude and refined products play a key part in the supply chain of hydrocarbons. Knowing the exact volume of these storage units plays a critical role when transferring products to and/or from the tanks. As a result of variations in external and internal conditions (i.e. temperature) and aging and also as a result of the weight of the liquid product (i.e. hydrostatic pressure), the tank volume can vary by as much as +/−0.2%. Considering a 250,000 barrel storage tank, this variation would result in a volume of +/−500 barrels in volume change.
As a result of the high value of petroleum hydrocarbons, there is a mandatory requirement for calibration of storage tanks. Tanks used for custody transfer must be calibrated such that the transferred volume is very accurately known (eg. Less than 0.1% error). The most commonly used techniques to perform this are; manual strapping (API MPMS 2.2A), optical techniques (Optical Reference Line Method ORLM—API Chapter 2.2B, Optical Triangulation Method (OTM)—API Chapter 2.2C, Electro-Optical Distance Ranging Method (EODR)—API Chapter 2.2D) and liquid calibrations (API Standard 2555). However, these measurements have been found to produce errors and are considered non-effective. In some cases, the foregoing testing techniques require tank downtime (e.g., emptying of the tank or otherwise halting the tank operation temporarily), which accumulates additional costs to the losses incurred. Moreover, many of the foregoing testing techniques are invasive in that they require accessing the internal volume of the tank and also can be destructive.
The existing methods for tank calibration present significant drawbacks. For instance, using the current standards, it can take 1-2 days of work to perform the calibration. As a result, calibration of storage tanks is performed infrequently thus leading to inaccurate measurements of the actual volume stored within the tank or transferred to and from the tank, which can be costly. For example, a traditional timeframe between calibrations can be between five and fifteen years.
Accurately measuring the dimensions of large structures like storage tanks can require a measuring instrument having a significant length which is known to a high degree of accuracy and which is used to measure the dimensions of the structure. However, existing measuring instruments of significant length (eg. 50 m) can experience physical expansion/contraction due to a variety of environmental factors, including, most notably, temperature. Accordingly, in order to perform highly precise measurements with such instruments, these measuring devices can require periodic calibration. In addition, the physical expansion/contraction of the device is often also approximated mathematically based on the environmental conditions during the instruments use.
What is needed are measuring systems and methods that addresses the limitations associated with the efficiency of performing measurements using existing systems. It is with respect to these and other considerations that the disclosure made herein is presented.